Swiss explorer unveils solar-powered plane

It has the wingspan of a Boeing 747 but weighs less than a small car. And it is powered entirely by the sun.

Adventurer Bertrand Piccard on Friday unveiled the Solar Impulse, which with its sleek white wings and pink trimming aims to make history as the prototype for a solar-powered flight around the world.

"Yesterday it was a dream, today it is an airplane, tomorrow it will be an ambassador of renewable energies," said Piccard, who in 1999 co-piloted the first round-the-globe non-stop balloon flight.

The plane will take part in a series of test flights over the next two years, and based on the results of those, a new plane will be constructed for the big takeoff, in 2012.

In a swank ceremony at a military airfield near Zurich, Piccard and co-pilot Andre Borschberg hugged as the curtain was pulled across to give the public its first glimpse of the plane. Numerous dignitaries were in attendance, including Prince Albert of Monaco and major sponsors.

The budget for the project is 70 million euros ($113 million Cdn), Piccard said.

Around-the-world flight a long-term goal

Piccard and Borschberg said the plane will fly day and night using almost 12,000 solar cells, rechargeable lithium batteries and four electric motors. It will not use an ounce of fuel.

But the maiden flight around the planet will take time.

With the engines providing only 40 horsepower, the plane will fly almost like a scooter in the sky. It will take off at the pedestrian pace of 35 km/h, accelerating at altitude to an average flight speed of 70 km/h.

For that reason, Piccard's circumnavigation will be split up into five stages. Borschberg said the stages are five days long because of the cockpit, which was made non-pressurized to keep the weight down.

"You can see it's really small," he said. "Thirty-six hours is already a challenge. It tests your patience."

The first test flights will be later this year, with a complete night voyage planned for 2010.

"It will be like the Wright brothers," said the 51-year-old Piccard, who comes from a long line of adventurers. His late father Jacques plunged deeper beneath the ocean than any other man, and grandfather Auguste was the first man to take a balloon into the stratosphere.

Clear skies needed for solar flight

"We will start one metre above the ground, then three metres, then five metres," he said. "When that works, we'll be able to take it to altitude."

One thing a solar plane cannot handle is bad weather. Because the solar panels are needed for day flying and for charging the 400-kilogram lithium batteries that power the plane by night, it relies on sunshine.

"We'll certainly avoid stormy situations," Borschberg said. "We'll avoid rain as well, because you cannot collect energy in this weather. So the challenge for the team will be to find a path that is favorable. We've been training for five years."

Piccard says the plane should also serve as an inspiration for inventors and manufacturers of everyday machines and appliances.

"If an aircraft is able to fly day and night without fuel, propelled solely by solar energy," Piccard said, "let no one come and claim that it is impossible to do the same thing for motor vehicles, heating and air conditioning systems and computers."